Growing up on The Accord, a young half elf from the village named Halborin was her “first love". He grew up in a dirt poor low status family, and convinced her to play hooky and do minor vandalisms. After a while, he filled her head with the desire to play Robin Hood, and after the first real robbery she realized she was trapped as a member of his gang. After a few years, she figured a way to escape, which you guess means she had some evidence to hold over him or something like that that she doesn’t really explain.

A few years go by with her spending a good part of her money on the local poor to help her guilt, but then her old lover shows up and threatens her. After she stands up to him, he leaves. A few days go by and she learns her younger brother has been kidnapped with a ransom note. As a trained first level bard, she convinces some of her friends to head to her old hangout and end this once and for all: go there kill him and free her brother. When she shows up she is surprised to find he has a small gang with him and things go very wrong. He happily admits that her younger brother has been killed, and the body disposed of, totally out of spite. In the fight that follows Halborin is able to escape, and she is left to deal with the results of her mistakes. With her guilt and shame, she had to leave the island.

This is why she left the Accord.
This is why she was on a boat in the first place.
This is why she was kidnapped.
Her whole time with the party has been a kind of self-imposed scourging punishment for her sins.

Maybe someday she can kill Halborin, but while that would be Justice that won't end her guilt.